Impingement refers to mechanical compression and/or wear of the rotator cuff tendons. The rotator cuff is actually a series of four muscles connecting the scapula (shoulder blade) to the humeral head (upper part of the shoulder joint). The rotator cuff is important in maintaining the humeral head within the glenoid (socket) during normal shoulder function and also contributes to shoulder strength during activity. Normally, the rotator cuff glides smoothly between the undersurface of the acromion, the bone at the point of the shoulder, and the humeral head. Any process which compromises this normal gliding function may lead to mechanical shoulder impingement.
Causes of Shoulder Impingement
Shoulder impingement is a frequent source of pain in adults. Common causes of shoulder impingement include:
- Weakening and degeneration within the tendon due to aging.
- The formation of bone spurs and/or inflammatory tissue within the space above the rotator cuff.
- Overuse injuries caused by repetitive movement and stress on the joint. Athletes and other workers who use repetitive overhead movement (i.e. swimmers, baseball players, tennis players, painters, and construction workers) are more susceptible of developing this condition.
- Acute trauma from a fall or impact to the shoulder joint.
Symptoms and Diagnosis
Patients with impingement most commonly complain of:
- Pain in the shoulder, which is worse with overhead activity and sometimes is severe enough to cause awakening in the night
- Difficulty reaching up behind the back
- Weakness of shoulder muscles
The diagnosis of shoulder impingement can usually be made with a careful history and physical exam. Manipulation of the shoulder in a specific way by your physician will usually reproduce the symptoms and confirm the diagnosis.
X-rays are also helpful in evaluating the presence of bone spurs and/or the narrowing of the subacromial space. MRIs are usually not necessary to diagnose shoulder impingement but may be used to rule out more serious diagnoses.
The first step in treating shoulder impingement is eliminating any identifiable cause or contributing factor. This may mean temporarily avoiding activities with repetitive overhead movements. A non-steroidal anti-inflammatory medication may also be helpful. The primary source of treatment involves exercises to restore normal flexibility and strength to the shoulder, including strengthening both the rotator cuff muscles and the muscles responsible for normal movement of the shoulder blade. On occasion, an injection of cortisone may prove to be helpful in treating this condition.
In most cases, surgery is not necessary for treatment of shoulder impingement. However if symptoms continue after trying proper nonsurgical treatment options, surgery could be beneficial. Typically, the surgery would involve removing the tissue that is causing irritation to the shoulder. This is done by either open or arthroscopic procedures with the outcome being favorable in more than 90% of the cases.
An exercise or physical therapy program usually begins the week after surgery, and will continue for eight to ten weeks. Most patients can return to work one to two weeks after surgery, depending on their job requirements. Full recovery for most patients is achieved within three to five months following surgery.